Polynomial expressions for Bickley and Exponential integral functions

In this paper a general polynomial expression is obtained for the Bickley and Exponential integral functions (Kin and En, n = 1-7), where only coefficients are different. These coefficients can be obtained, depending on the accuracy we require. One problem of a homogeneous reactor has been considered here where it is shown that a polynomial of limited accuracy also can give converged results, depending upon the problem.